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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Thermodynamic Modeling of the Al-Ce-Cu-Mg-Si System and Its Application to Aluminum-Cerium Alloy Design

Recently discovered AlCe alloys have shown promise in a number of applications, but the propensity of Ce to react with Al and other alloying elements can complicate the phase equilibria and design approach. To solve this, the CALPHAD method is used to explore an alloy within the quinary Al-Ce-Cu-Mg-Si system by developing a thermodynamic database with self-consistent parameters. The database includes a description of all 10 binary systems and 8 ternary systems consisting of: (i) 6 Al-containing ternaries (Al-Ce-Cu, Al-Ce-Mg, Al-Ce-Si, Al-Cu-Mg, Al-Cu-Si and Al-Mg-Si); and (ii) 2 additional ternaries that include Mg and Si (i.e., Ce-Mg-Si and Cu-Mg-Si). The thermodynamic description for the Al-Ce-Mg and Al-Mg-Si systems were reassessed to ensure consistency with the binary systems and the Ce-Mg-Si system is presented for the first time and compared to theoretical data from DFT (Density Functional Theory). In addition to the ternary interactions, the quaternary compound Al3Cu2Mg9Si7 and solid solution extending from the ternary Al2CuMg phase (Al,Si)2CuMg are incorporated. The CALPHAD method is employed and leveraged through the use of a Materials Design Simulator (MDS) to accelerate the design of novel aluminum-cerium-based alloys. The combination of a CALPHAD-based framework with experimental efforts and industrial insight permits the development of three new Al-Ce alloys: Al-3.5Ce-0.4Mg-7Si (Ce-modified A356), Al-5Ce-1Cu-0.5Mg-10Si and Al-19Ce-0.9Mg-1.1Si.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce(MgSi)2 by Materials Project

CeMg2Si2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Mg2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Mg–Si bond lengths are 2.75 Å. Ce4+ is bonded to eight equivalent Si4- atoms to form a mixture of edge and face-sharing CeSi8 hexagonal bipyramids. All Ce–Si bond lengths are 3.19 Å. Si4- is bonded in a 9-coordinate geometry to four equivalent Mg2+, four equivalent Ce4+, and one Si4- atom. The Si–Si bond length is 2.29 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeMgSi2 by Materials Project

CeMgSi2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Mg is bonded in a distorted square co-planar geometry to four Si atoms. There are two shorter (2.75 Å) and two longer (2.76 Å) Mg–Si bond lengths. Ce is bonded in a 10-coordinate geometry to ten Si atoms. There are a spread of Ce–Si bond distances ranging from 3.09–3.20 Å. There are eight inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to four equivalent Mg, four equivalent Ce, and one Si atom. All Si–Ce bond lengths are 3.16 Å. The Si–Si bond length is 2.31 Å. In the second Si site, Si is bonded in a 9-coordinate geometry to four equivalent Mg, four equivalent Ce, and one Si atom. The Si–Si bond length is 2.31 Å. In the third Si site, Si is bonded in a 9-coordinate geometry to four equivalent Mg, four equivalent Ce, and one Si atom. There are two shorter (2.75 Å) and two longer (2.76 Å) Si–Mg bond lengths. All Si–Ce bond lengths are 3.16 Å. The Si–Si bond length is 2.31 Å. In the fourth Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ce and three Si atoms. There are two shorter (3.09 Å) and four longer (3.20 Å) Si–Ce bond lengths. Both Si–Si bond lengths are 2.35 Å. In the fifth Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ce and three Si atoms. Both Si–Si bond lengths are 2.35 Å. In the sixth Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ce and three Si atoms. The Si–Si bond length is 2.31 Å. In the seventh Si site, Si is bonded in a 9-coordinate geometry to four equivalent Mg, four equivalent Ce, and one Si atom. There are two shorter (2.75 Å) and two longer (2.76 Å) Si–Mg bond lengths. All Si–Ce bond lengths are 3.16 Å. The Si–Si bond length is 2.31 Å. In the eighth Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ce and three Si atoms. There are two shorter (3.09 Å) and four longer (3.20 Å) Si–Ce bond lengths. There are one shorter (2.31 Å) and two longer (2.35 Å) Si–Si bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce2MgSi2 by Materials Project

MgCe2Si2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Mg2+ is bonded in a square co-planar geometry to four equivalent Si4- atoms. All Mg–Si bond lengths are 2.93 Å. Ce3+ is bonded in a distorted hexagonal planar geometry to six equivalent Si4- atoms. There are two shorter (3.02 Å) and four longer (3.08 Å) Ce–Si bond lengths. Si4- is bonded in a 9-coordinate geometry to two equivalent Mg2+, six equivalent Ce3+, and one Si4- atom. The Si–Si bond length is 2.40 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CeMg6Si by Materials Project

Mg6CeSi crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 12-coordinate geometry to eight Mg, two equivalent Ce, and two equivalent Si atoms. There are a spread of Mg–Mg bond distances ranging from 3.04–3.41 Å. There are one shorter (3.21 Å) and one longer (3.41 Å) Mg–Ce bond lengths. Both Mg–Si bond lengths are 3.14 Å. In the second Mg site, Mg is bonded to ten Mg and two equivalent Ce atoms to form distorted MgCe2Mg10 cuboctahedra that share corners with four equivalent CeMg10Si2 cuboctahedra, corners with six equivalent MgCe2Mg10 cuboctahedra, edges with two equivalent CeMg10Si2 cuboctahedra, edges with four equivalent MgMg10Si2 cuboctahedra, faces with two equivalent CeMg10Si2 cuboctahedra, and faces with four MgCe2Mg10 cuboctahedra. There are four shorter (3.08 Å) and two longer (3.13 Å) Mg–Mg bond lengths. Both Mg–Ce bond lengths are 3.29 Å. In the third Mg site, Mg is bonded in a 12-coordinate geometry to eight Mg, two equivalent Ce, and one Si atom. There are a spread of Mg–Mg bond distances ranging from 3.08–3.48 Å. Both Mg–Ce bond lengths are 3.25 Å. The Mg–Si bond length is 3.23 Å. In the fourth Mg site, Mg is bonded to ten Mg and two equivalent Si atoms to form distorted MgMg10Si2 cuboctahedra that share corners with six equivalent MgMg10Si2 cuboctahedra, edges with four equivalent MgCe2Mg10 cuboctahedra, faces with four MgCe2Mg10 cuboctahedra, and faces with six equivalent CeMg10Si2 cuboctahedra. Both Mg–Si bond lengths are 3.28 Å. Ce is bonded to ten Mg and two equivalent Si atoms to form distorted CeMg10Si2 cuboctahedra that share corners with four equivalent MgCe2Mg10 cuboctahedra, corners with six equivalent CeMg10Si2 cuboctahedra, edges with two equivalent MgCe2Mg10 cuboctahedra, faces with two equivalent CeMg10Si2 cuboctahedra, and faces with eight MgCe2Mg10 cuboctahedra. Both Ce–Si bond lengths are 3.00 Å. Si is bonded in a 2-coordinate geometry to eight Mg and two equivalent Ce atoms.

36 MATERIALS SCIENCE↗